minimize ambient occlusion

Im color correcting some 3d footage. i forgot to put the ambient occlusion in a separate pass. i now have a grey color in the footage that i would like to minimize and/or remove.

so..

what's the best method to even out a little to dark grey colortone in a very specific area?
i tried to mask out and apply curves. gave okay results but i feels like there should be a more 'correct/easier/pro' way to do it.

One option, would be to go ahead and render that separate ambient occlusion pass now. When it's done, place it over the heavily occluded footage in your comp and set it's blend mode to 'Divide' (only available in CS5+) or add an 'Invert' effect and set the blend mode to 'Color Dodge' (available in previous versions, same result). That should entirely remove the ambient occlusion (except where your image is pure black, if it's a very dark render then this technique may not work).

You can then reduce the opacity of the separate ambient occlusion pass to bring back some of the ambient occlusion. Alternatively you can apply a Levels effect to the separate pass and increase the Black Output or Gamma values to tweak not only how intense the ambient occlusion is, but how quickly it falls off as well (Gamma).

I found it a good suggestion too Darby. As somewhat of a newb to C4D multipass, I've stumbled across a few of your posts in the last week that have been very useful to me. Keep up the good work my friend, your efforts are not in vain!